Scientific ocean drilling poised to reveal the secrets of the subseafloor for the next decade

IODP-Management International (IODP-MI) today announced the successful conclusion of the CHIKYU+10 International Workshop held in Tokyo, Japan, from 21-23 April 2013.

The event, convened by the global scientific ocean drilling community and enabled by the Japan Agency for Marine-Earth Science and Technology, focused on Chikyu’s explorations for the next decades in pursuit of new knowledge about Earth’s past and innovative research into today’s global challenges.

“Chikyu will be a keystone of the IODP endeavor for the next decade and beyond, providing the global research community with the capability to reach deep targets inaccessible by any other scientific platform.” says Prof.

Mike Coffin, University of Tasmania, Australia, and Chair of the CHIKYU+10 Steering Committee.

About 400 scientists and engineers from over 20 countries attended the workshop, including senior officials from funding agencies MEXT (Japan’s Ministry of Education, Culture, Sports, Science and Technology) and NSF (U.S. National Science Foundation), representatives of IODP partners, and scientists from 180 prominent universities and other institutions worldwide. The workshop was hosted by CDEX (Center for Deep Earth Exploration of JAMSTEC) assisted by IODP-MI.

“The Workshop was a landmark success. I saw so many new faces from around the world. Workshop participants clearly consider Chikyu as an international scientific asset.” said Kiyoshi Suyehiro, President and C.E.O. of IODP-MI.

Four Co-Chief Scientists of past Chikyu expeditions also made presentations highlighting their teams’ research and describing the transformational capabilities Chikyu offers the Earth, ocean, and life sciences communities. Presentations covered not only the first 10 years of successful Chikyu operations, but also Chikyu’s continued importance to international scientific ocean drilling research in the next decades.

The workshop focused on five thematic areas identified from short white papers accepted in early 2013: Active Faults, Ocean Crust and Earth’s Mantle, Deep Life and Hydrothermal Systems, Continent Formation, and Sediment Secrets.

Thematic discussions highlighted accomplishments of Chikyu’s completed expeditions, proposals to use Chikyu’s deep riser capability, new ideas submitted from the community, and inspiring keynote talks. Deliberations among researchers will help prioritize projects for Chikyu’s next decade of exploration and beyond.

Global climate change, earthquakes, and tsunami generation are some of the most pressing societal research challenges of the 21st century. At the workshop, the scientific community affirmed that Chikyu will continue to play an important role as a key platform for scientific ocean drilling to investigate these phenomena and fundamental questions in Earth, ocean, and life sciences.

Scientific ocean drilling poised to reveal the secrets of the subseafloor for the next decade

IODP-Management International (IODP-MI) today announced the successful conclusion of the CHIKYU+10 International Workshop held in Tokyo, Japan, from 21-23 April 2013.

The event, convened by the global scientific ocean drilling community and enabled by the Japan Agency for Marine-Earth Science and Technology, focused on Chikyu’s explorations for the next decades in pursuit of new knowledge about Earth’s past and innovative research into today’s global challenges.

“Chikyu will be a keystone of the IODP endeavor for the next decade and beyond, providing the global research community with the capability to reach deep targets inaccessible by any other scientific platform.” says Prof.

Mike Coffin, University of Tasmania, Australia, and Chair of the CHIKYU+10 Steering Committee.

About 400 scientists and engineers from over 20 countries attended the workshop, including senior officials from funding agencies MEXT (Japan’s Ministry of Education, Culture, Sports, Science and Technology) and NSF (U.S. National Science Foundation), representatives of IODP partners, and scientists from 180 prominent universities and other institutions worldwide. The workshop was hosted by CDEX (Center for Deep Earth Exploration of JAMSTEC) assisted by IODP-MI.

“The Workshop was a landmark success. I saw so many new faces from around the world. Workshop participants clearly consider Chikyu as an international scientific asset.” said Kiyoshi Suyehiro, President and C.E.O. of IODP-MI.

Four Co-Chief Scientists of past Chikyu expeditions also made presentations highlighting their teams’ research and describing the transformational capabilities Chikyu offers the Earth, ocean, and life sciences communities. Presentations covered not only the first 10 years of successful Chikyu operations, but also Chikyu’s continued importance to international scientific ocean drilling research in the next decades.

The workshop focused on five thematic areas identified from short white papers accepted in early 2013: Active Faults, Ocean Crust and Earth’s Mantle, Deep Life and Hydrothermal Systems, Continent Formation, and Sediment Secrets.

Thematic discussions highlighted accomplishments of Chikyu’s completed expeditions, proposals to use Chikyu’s deep riser capability, new ideas submitted from the community, and inspiring keynote talks. Deliberations among researchers will help prioritize projects for Chikyu’s next decade of exploration and beyond.

Global climate change, earthquakes, and tsunami generation are some of the most pressing societal research challenges of the 21st century. At the workshop, the scientific community affirmed that Chikyu will continue to play an important role as a key platform for scientific ocean drilling to investigate these phenomena and fundamental questions in Earth, ocean, and life sciences.

Scientists obtain rocks moving into seismogenic zone

Scientists document and sample cores. -  JAMSTEC/IODP
Scientists document and sample cores. – JAMSTEC/IODP

An international group of scientists aboard the Deep-Sea Drilling Vessel CHIKYU, operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) for the Integrated Ocean Drilling Program (IODP), return from a 40-day scientific expedition off the shore of the Kii Peninsula, Japan on Oct. 10, 2009. Expedition 322, called “Subduction Inputs” in the multi-stage project, conducted drilling, logging and sampling beneath the ocean floor to investigate input material that will be transported to the seismogenic zone by the plate subduction system.

The drilling operations were carried out at two sites in the Shikoku Basin, the back-arc basin of the Izu-Bonin volcanic chain where the Philippine Sea Plate dives down into the Nankai Trough at a rate of about 4 cm per year. At the first site C0011, scientists began coring from a depth of 340 meters below the seafloor. The coring, however, had to be abandoned at a depth of 881 meters because of damage of the drill bit. At the second site C0012, coring was carried out from depths 60 meters to 576 meters below the seafloor, and successfully collected the targeted sedimentary and basement rock samples.

Dr. Michael Underwood, professor at University of Missouri, USA, and co-Chief Scientists of the expedition said, “We identified an interface of Miocene sediment and basement rock around 540 meters beneath the seafloor and successfully sampled basaltic pillow lava rocks that make up the basement.” He added “These sedimentary and volcanic rocks in the lower part of Shikoku Basin are key intervals for generating large earthquake slip after they are transported to the seismogenic zone. Studying their petrological, geotechnical, frictional and hydrogeological properties prior to subduction is expected to contribute significantly to the understanding of rupture dynamics in the seismogenic zone.”

The science party included 26 onboard research specialists from international member countries. “Scientists observed, measured and analyzed geological samples by day and night working shifts in the onboard laboratories,” said Dr. Saneatsu Saito from JAMSTEC who led research activities as another co-Chief Scientist. He explained the importance of the variety of data obtained, “The sand-rich volcanic sediments were confirmed in large quantity and may have been transported from the easterly located Izu-Bonin Arc about 5 to 11 million years ago. Other sandstones contain abundant minerals derived from land, implying the extensive supply of sand to the Shikoku Basin from the Japanese islands.” Prof. Underwood added, “Analysis of pore water and hydrocarbon gases retrieved from the sedimentary layers above the basement indicates multiple sources and migration paths of fluids. These results have important implications for understanding the properties of fluids within the seismogenic zone.”

Scientists return from first ever riser drilling operations in seismogenic zone

This image shows a worker lowering the tool to measure stress and pore fluid pressure in the subsurface. -  Copyright: JAMSTEC/IODP
This image shows a worker lowering the tool to measure stress and pore fluid pressure in the subsurface. – Copyright: JAMSTEC/IODP

The Deep-sea Drilling Vessel CHIKYU successfully completed riser drilling operations on Aug. 31, for IODP Expedition 319, Stage 2 of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE). The CHIKYU is operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in partnership with the Integrated Ocean Drilling Program. The expedition began with drilling operations at the Kumano Basin, off the Kii Peninsula on May 10, 2009. Expedition 319 marks the first riser drilling in the history of the scientific ocean drilling program, and the first subseafloor observatory operations for NanTroSEIZE. The expedition was led by four Co-Chief Scientists: Eiichiro Araki, Research Scientist of JAMSTEC; Timothy Byrne, Professor of the University of Connecticut, USA; Lisa McNeill of the University of Southampton, UK; and Demian Saffer, Associate Professor of Geosciences at The Pennsylvania State University, and was joined by scientists from eight countries.

Expedition 319 conducted drilling operations at three drill sites in the Nankai Trough. At the first Site C0009, located directly above the seismogenic zone where great earthquakes occur, scientists conducted the first riser drilling in IODP history and successfully drilled down to a depth of 1,603.7 meters beneath the sea floor. Riser-based drilling allowed the scientists to conduct several scientific operations unprecedented in IODP, including 12 successful measurements of stress and pore fluid pressure in the subsurface using the dynamic formation testing tool, a two ship seismic experiment using a dense seismic array in the borehole, real-time mud gas analysis, and laboratory analyses of drill cuttings that are generated as the drill bit penetrates through the formation. In addition, 57.87 meters of core sample (a cylindrical geological sample) were obtained from depths between 1,510 and 1,593.9 meters below the seafloor. The scientific party developed several new techniques for analyzing these materials, which will be essential for future riser-based drilling.

The stress and pore pressure measurements are critical to understanding the mechanics of active tectonic fault zones, but have previously been unavailable in the scientific ocean drilling. Successful deployment of the test tool to measure these quantities deeper within the upper plate and near major fault zones in future riser holes will constitute a major breakthrough in understanding subduction zone fault earthquakes.

Also a walk-away Vertical Seismic Profiling (VSP) involving the CHIKYU and JAMSTEC’s Research Vessel KAIREI was conducted to characterize the structure of the seismogenic plate boundary below the borehole by utilizing an array of seismic sensors temporarily clamped inside the borehole. Air guns towed by the KAIREI generated seismic waves, and reflected seismic waves from the fault system were clearly observed by the borehole sensors. Experience from the VSP experiment will open the way to in-depth study of seismogenic faults that are beyond the reach of drilling.

At a second borehole (Site C0010), drilling crossed one of the major faults in the plate boundary, known as the mega-splay fault, at a depth of about 400 meters below the seafloor. This fault is a prime candidate for tsunami generation, and may have slipped in historical great earthquakes. During the drilling operation, scientists documented rock physical properties and gained information about stresses in the formation. The borehole was then cased and utilized for observatory operations for future long-term borehole monitoring. These included lowering of test instruments, as well as emplacement of a temporary sensor package that will monitor conditions in the fault zone in the next few years.

The new data from Expedition 319 indicate that the stresses in the upper plate reflect the forces acting on the earthquake generating fault zones below. The direction of the maximum stresses follows the direction of tectonic plate motion in most of the region, but rotates drastically in a very narrow region above the mega-splay fault. In addition, the rock units, and in particular the ages of the rocks obtained by examining microfossils and the sediment types observed in the drill cuttings, provide new constraints on the geologic history of the major fault zone and its activity level.

The CHIKYU is now berthed at the Port of Yokkaichi, where it is preparing for IODP Expedition 322 scheduled to sail on Sept. 4. Operations will include core sampling and logging for all layers in the formation, with an aim to better understand the initial state of geological input materials before they are entering the seismogenic zone.

Researchers report successful riser-drilling operations in seismogenic zone

Lead scientists Lisa McNeill and Tim Byrne examine core retrieved from beneath the sea floor, from an earthquake-generating zone called the Nankai Trough, off the coast of Japan. -  JAMSTEC/IODP
Lead scientists Lisa McNeill and Tim Byrne examine core retrieved from beneath the sea floor, from an earthquake-generating zone called the Nankai Trough, off the coast of Japan. – JAMSTEC/IODP

Kumano Basin off Kii Peninsula, approximately 58 km southeast of Japan- Despite harsh atmospheric and ocean conditions, and complex geological characteristics of its drill site, the deep-sea drilling vessel CHIKYU, for the first time in the history of scientific ocean drilling, conducted riser-drilling operations to successfully drill down to a depth of 1,603.7 meters beneath the sea floor (at water depth of 2,054 meters). Engaged in IODP Expedition 319, the CHIKYU is drilling deep into the upper portion of the great Nankai Trough earthquake zone to gain insights into geological formations and stress-strain characteristics. The CHIKYU is operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) a partner in the Integrated Ocean Drilling Program (IODP). The Kumano Basin drilling and sampling operations began on May 12; the science party is expected to complete the first drill site on or about August 1.

Riser-drilling technology was employed from about 700 meters below the sea floor to the bottom of the hole. Riser-drilling involves the circulation of drilling fluid that helps maintain pressure balance within the borehole. Cuttings were recovered from the circulated drilling fluid and analyzed to gain a better overall picture of downhole changes in lithology and age. Core samples also were collected between depths of 1,510 and 1,593.3 meters below the seafloor.

Co-Chief Scientist Lisa McNeill of University of Southampton, UK, states, “This state-of-the-art technology enables scientists to access an unknown area. It will provide a lot of important information about what has happened in the seismogenic zone in the past and its present condition.” She adds, “I’m very pleased to be a member of the science party conducting the first riser-drilling operation in the Nankai Trough.”

Following drilling operations that included “measurement -while-drilling” to obtain real-time geophysical characteristics, wireline logging instruments were lowered into the borehole to measure formation temperature, resistivity, porosity, density, gamma ray, and borehole diameter. The riser-drilling technology enabled dynamic formation testing using the logging instrumentation for the first time during IODP scientific ocean drilling operations; this instrumentation is designed to measure stress, water pressure, and rock permeability.

Co-Chief Scientist Timothy Byrne of University of Connecticut emphasizes the importance of the Nankai Trough experiment results. “These two parameters , stress magnitude and pore pressure,” he says, “are both important to understanding earthquake processes.”

In addition, vertical seismic profiling was conducted from July 24󈞅 to obtain accurate details of the geological structure of the plate boundary system. The activity involved an array of 16 seismographs vertically lowered into the borehole and eight ocean-bottom seismographs placed on the sea floor. An air-gun array on the JAMSTEC research vessel KAIREI generated elastic waves, which traveled through the formation to be recorded on the borehole and sea floor instruments.

“The seismic sensor array was installed in this hole below the thick sediment layer,” says Co-Chief Scientist Eiichiro Araki of JAMSTEC. “It acts like a telescope exploring the structure of faults in detail, which are responsible for causing large earthquakes such as the one that occurred here in 1944.”

Operations at this drill site are expected to conclude after casing the borehole to the bottom of the hole and capping it with a corrosion cap for future installation of a long-term borehole monitoring system (LTBMS). After completion of this task, the CHIKYU will move to its next drill site, where riserless drilling will be employed to penetrate the shallow portion of the megasplay fault branching from the seismogenic zone. Logging-while-drilling (LWD) will be conducted to measure rock properties, geological formation, and geophysical characteristics of the area. As a preliminary operation for LTBMS scheduled in the future, observatory instruments will be installed inside the hole to measure borehole temperature and pressure over the next few years.

Further analyses are expected to generate significant scientific knowledge of past earthquake activities and development processes of the Nankai Trough accretionary prism, as well as the mechanism of occurrence of large earthquakes and tsunamis.

Co-Chief Scientist Demian Saffer of The Pennsylvania State University notes, “With the efforts of the drillers and operations groups, we succeeded in conducting several very challenging experiments, many of which can only be achieved by riser drilling. The results provide important information about conditions within the rocks above zones where earthquakes occur. Ultimately, we plan to install long-term observatory systems in these boreholes that will allow us to continuously monitor the geologic formation during the earthquake cycle.”

First riser-drilling research operations undertaken

Approximately 58 km southeast of Shingu City, Japan–Deepsea Drilling Vessel CHIKYU has resumed IODP drilling operations in the Nankai Trough Seismogenic Zone off the Kii Peninsula of Japan. The scientific drilling expedition’s first target is located in water depths of 2,054 meters. Following sea floor surveys, the crew began fitting riser pipe and a blow-out prevention (BOP) system into an upper section of the first borehole to be drilled. The riser pipe and BOP (the blow-out preventer) was successfully connected to the wellhead. After testing the circulation of the drilling fluid, the first riser-drilling operations for CHIKYU in the history of scientific ocean drilling began. The British Broadcasting Corporation (BBC) chronicled the lead-in to this historic activity, the first media organization outside Japan to broadcast live from aboard CHIKYU.

The target drilling depth at the first borehole is 1,600 meters below the seafloor. Following drilling operations, vertical seismic profiling (VSP) is expected to begin as part of geophysical logging.

Riser-drilling involves a large marine riser pipe that connects the CHIKYU to the seafloor. The riser pipe guides the drill pipe as it reenters the well. Drilling fluid is pumped up and down between the riser pipe and the drill pipe. Fluid circulation and use of the blow-out preventer (BOP) help to maintain pressure balance within the borehole and prevent it from collapsing, enabling safer and deeper drilling.

CHIKYU is the world’s first scientific drilling vessel capable of riser-drilling deep beneath the ocean floor and in seismogenic (earthquake-producing) zones that have never been reached before.

The Nankai Trough subduction zone, located southwest of Japan, is one of the most active earthquake zones on the planet, with complex geological formations caused by tectonic plate thrusts. The scheduled drill site, the Kumano Basin, is a fore-arc basin of the Nankai Trough under the influence of the strong Kuroshio ocean current. In combination with inclement weather expected, due to passing typhoons, and riser drilling down to depths of more than 2,000 meters below surface, this phase of NanTroSEIZE is considered one of the most challenging tasks in ocean-drilling history.

The average speed of the Kuroshio current in the surveyed area is about 1.0 knots, relatively slow for the current speed usually observed in the Kumano Basin. Yet, fairings are to be mounted onto to a riser pipe to smooth the hydrodynamic flow behind the riser pipe (to reduce riser drag) and suppress the vortex-induced vibration under high current conditions. The motion of the riser also will be monitored for analysis, in order to use the results in future operations.